This invention relates in general to those structures in which a skeleton frame supports a fabric canopy to provide a shelter and more particularly to the structures of this type in which the skeleton frame is modular so that it can readily be erected and taken down and so that it can be easily transported in a disassembled state.
The purpose of all of these structures is to provide a readily transportable, relatively inexpensive structure which can be erected at a site quickly, at minimum cost and without requiring extensive or expensive construction equipment.
The purpose of this invention is to provide an improved structure which meets all of these objectives in an enhanced fashion.
More particularly, it is a purpose of this invention to provide such a structure in which there is an enhanced trade off of cost, transportability and ease of erection.
These structures, which are tent type structures, generally require guy-wires and support mechanisms that are anchored away from the area covered by the tent-like structure in order to provide stability for the structure. Wind loading and the modular nature of the structure create stability problems. For reasons of cost, ease of construction, and ease of disassembling, it is desirable that the modular portions not be too elaborately interconnected. As a consequence, there is a tendency for the structure to be somewhat unstable and to at least require extensive auxiliary support members such as posts and rails and support wires. These auxiliary structures are either outboard of the area covered by the shelter and thus require a more extensive ground plot than is sheltered, or inboard of the structure thus limiting use of the interior space.
Accordingly, it is another purpose of this invention to provide a structure which meets the above objectives and which also permits substantially covering an allocated ground plot without requiring substantial outboard or inboard supports.
The use of arches and fabric is one common way of meeting these objectives.
A number of patents to Karl S. Huddle illustrate the use of arches and fabric including U.S. Pat. No. 3,215,153 issued Nov. 2, 1965; U.S. Pat. No. 3,811,454 issued May 21, 1974; and U.S. Pat. No. 3,899,854 issued Aug. 19, 1975.
The U.S. Pat. No. 3,811,454 illustrates the use of arches which are pivotally connected to a base as a labor saving feature. In this design the fabric is used to support or hold the arches in place.
The U.S. Pat. No. 3,899,854 illustrates a relevant design which incorporates various transverse compression members and interconnections that contribute to the cost of erection and disassembly.
The arch support structure shown in the Spray U.S. Pat. No. 3,892,094 issued June 1, 1975 is typical of a group of structures in which there is appreciable interconnection between arched rods to provide structual stability but which interconnections provide a substantial cost of construction and disassembly.
A single dual arch arrangement is illustrated in the Sperling U.S. Pat. No. 3,365,846 issued Jan. 30, 1968. Although Sperling suggests the use of a single dual arch arrangement either for the roof of a house or for the structure of a tent, Sperling does not obtain the large scale shelter which it is an object of this invention to provide.
For relatively small type structures to cover a relatively small area, the advantages of a tent type of arrangement is usually quite clear cut. But, when it is desired to provide a large structure, such as in a pavilion at a fair or one in which a sporting event can be performed while accommodating numerous spectators, the cost advantages of a frame supporting a flexible fabric skin may be outweighed by the costs of construction and the instability of the structure.
Accordingly, it is an important purpose of this invention to provide an improved flexible fabric shelter which can be used to cover a relatively large field and which can be built with enough height to comfortably accommodate large numbers of people by providing adequate air space as well as space to accommodate lighting, banners and the like.
It is a further important purpose of this invention to provide such a shelter which is also very safe and more particularly a shelter in which the safety of the shelter does not depend on the structual integrity of the fabric or the skin covering.